Tubular inductor structure for linear motors

ABSTRACT

An annular cylindrical inductor component of an electric motor of the linear type which comprises an annular assembly of radially extending and essentially flat sheets of a ferromagnetic material. The inner edge portions of the assembled sheets which form a cylindrical opening within which the motor armature is mounted for sliding movement are provided with longitudinally spaced notches which form cylindrical recesses within which the motor windings are located and the radially outer portions of the sheets are deformed in a direction perpendicular to the plane of the sheet to establish longitudinally extending spaces between adjacently contacting sheets. The deformations along the radially outer portions of the sheets can be established by a double-bending operation or these portions of the sheets can be provided with single or double ribs. Also, non-deformed sheets can be located between sheets which are deformed and which extend radially outward beyond the deformed sheets thus to function as cooling fins. The outer portions of the sheets may also be notched to establish one or more longitudinally spaced peripheral grooves within which a strand of solder, or ferrule or wire binding is located so as to bind the sheets together. Bearings for supporting the rotor can be mounted at the radially inner portion of the sheet assembly or these can be carried by endplates secured to the opposite ends of the sheet assembly.

31D-13 SR FIF8592. QR. 3 828g211 United States Patent 1191 1111 3,828,211

Laronze 5] Aug. 6, 1974 TUBULAR INDUCTOR STRUCTURE FOR tric motor of the linear type which comprises an annu- LINEAR MOTORS lar assembly of radially extending and essentially flat sheets of a ferro-magnetic material. The inner edge portions of the assembled sheets which form a cylindrical opening within which the motor armature is [75] inventor: Joseph Laronze, Tassin La Demi-Lune, France [73] Assignee: BBC Brown Boveri & Company mounted for sliding movement are provided with lon- Limited, Baden, Switzerland gitudinally spaced notches which form cylindrical recesses within which the motor windings are located [22] Flled' July 1973 and the radially outer portions of the sheets are de- [21] Appl. No.: 381,448 formed in a direction perpendicular to the plane of the sheet to establish longitudinally extending spaces between adjacently contacting sheets. The deformations Foreign Apphcatlon Pnomy Data along the radially outer portions of the sheets can be July 28, 1972 France 72.27956 established by a doublebending operation or these portions of the sheets can be provided with single or [52] US. Cl. 310/13, 310/ double ribs Also, nomdetbrmed Sheets can be located [51] 1111. CL H02k 41/02 between sheets which are deformed and which extend [58] new of Search 310/12 641 radially outward beyond the deformed sheets thus to 310/65; 179/115 -5 120 function as cooling fins. The outer portions of the sheets may also be notched to establish one or more [56] References C'ted longitudinally spaced peripheral grooves within which UNITED STATES PATENTS a strand of solder, or ferrule or wire binding is located 662,928 12/1900 Geisnlioner 310/65 so as to bind the Sheets together. Bearings for support- 3,435,262 3/1969 Bennett et al. ing the rotor can be mounted at the radially inner por- 3,599.020 8/1971 Harris et al. 310/13 tion of the sheet assembly or these can be carried by 3,723.779 3 3 endplates ecured to the pposite ends of the heet assembl Primary Examiner-Gerald Goldberg y Alrorney, Age/11, or Firm-Pierce. Schefflcr & Parker [57] ABSTRACT An annular cylindrical inductor component of an elec- 15 Claims, 19 Drawing Figures PAIENIEDAUE SL974 SHEET 1 BF 3 FIGS I PAIENIED 3.82821 1 sum 3 OF 3 TUBULAR INDUCTOR STRUCTURE FOR LINEAR MOTORS The present invention. relates to linear motors wherein the inductor is of tubular and generally cylindrical shape so as to surround the armature.

For inductors of that kind, the coils are located in transverse planes and therefore the flux circulates in longitudinal planes through the motor axis. A magnetic circuit division ensues, in order to avoid eddy currents, which ordinarily also should be in longitudinal planes. In other words, this circuit should be laminated longitudinally. However, this cannot be directly implemented because the longitudinal separating planes through the axis are not parallel and therefore do not lend themselves to the conventional solution of merely superposing sheets of regular thickness. Therefore it is generally preferred to achieve division along the transverse planes which, though definitely less advantageous, on the other hand eliminates all complications.

The present invention on the other hand aims to achieve a longitudinally laminated magnetic circuit without encountering any particular difficulty in so doing and by means of conventional sheets of constant thickness and for a tubular inductor of the kind mentioned and which will be compact with respect to diameter and for which the connections to the windings will present no problems at all, and which may be easily cooled.

In conformity with the invention, the magnetic circuit is achieved by the juxtaposition of flat sheets with edges notched in known fashion, the opposite edges of at least some of these being so formed as to be of larger transverse size than the thickness of the sheets being considered.

It will be observed that in view of the presence of the edges that were shaped as indicated above, juxtaposition of the sheets causes a hollow cylindrical volume in the inner part of which there will be a series of housings suitable to seat circular coils, whereas the small spaces separating the successive sheets maybe used for housing the means for connections and/or for passing coolmg air.

In a preferred embodiment, edge shaping is achieved by folding back in such manner that a laterally offset edge will be obtained, which is amenable to being oriented with respect to the plane of the non-deformed sheet at such an angle as to be in a plane essentially radial with respect to the cylinder finally obtained.

Depending on circumstance, one may restrict oneself to using only such flanged sheets or one may use any suitable combination of such sheets with those that are entirely flat. In the latter case, the flat sheets may advantageously be radially protruding so as to constitute cooling fins.

Obviously the sheets must bepreviously mounted on the windings because the final cylindrical shape of the circuit will prohibit any subsequent assembly. The operation may be achieved by means of a coil-former suitable for coil and sheet centering.

Lastly, it will be advantageous that the magnetic circuit built up as described above be provided with bearings suitable to assure sliding guidance of the motor armature. Particularly these bearings may be fastened to the end-shields fastened to the magnetic circuit or to the frame surrounding same.

The bearings also may be made of plastic with low coefficient of friction and be mounted in the magnetic circuit, notably in the manner of annular closing chocks for certain of the circuit notches. Such bearings also may be fastened by glueing or otherwise to the individual coil supports of the windings, or they may consist of the very base of that support. In any event, following inductor assembly, it will be enough to pass a broach through it in order to ream and center the bearings.

The attached drawing is provided for illustrative purposes and so as to provide better insight into the invention and of its characteristics and likely advantages.

FIG. 1 shows a sheet for the construction of the magnetic circuit of a field of tubular shape in conformity with the invention, following notching at one edge of the sheet but prior to flanging of the opposite edge.

FIG. 2 is a perspective of the sheet of FIG. 1 after flanging of its notch-free longitudinal edge.

FIG. 3 is a front-view showing the juxtaposition of sheets of FIG. 2 in order to achieve a magnetic circuit for a tubular inductor.

FIG. 4 is a perspective with a fragmentary view showing the linear motor with a tubular inductor of FIG. 3.

FIG. 5 is similar to FIG. 3 but includes a variation.

FIGS. 6 and 7 are transverse sections showing the juxtaposition of radially oriented sheets with respect to a common axis, there being no flanging for the sheets of FIG. 6, while FIG. 7 shows flanging in conformity with the invention.

FIG. 8 is a partial side-view of an embodiment wherein the sheets are notched at their flanged edges so as to achieve circular grooves on the circumference of the inductor after assembly.

FIG. 9 shows a sheet before flanging, the edge opposite the notches having stamped apertures so as to achieve the grooves of FIG. 8.

FIG. 10 shows the same sheet upon being folded back.

FIG. 1 is similar to FIG. 8 but with the addition of the grooves having been filled with weld beads.

FIG. 12 is a section through a variation in which each groove is provided with a tightening loop.

FIGS. 13 and 14 show two variations in the method of shaping the edges opposite the notches.

FIGS. 15 through 19 are partial longitudinal sections showing various bearings for a linear motor comprising a tubular inductor in conformity with the invention.

With reference now to FIG. 1 a flat sheet 1 is shown in the shape of an elongated rectangle, with notches 2 to house the motor windings in the known manner of linear motors with flat armatures, these notchesdetermining intermediate teeth 3 between them. The thickness of sheet 1 is constantand the material is suitably magnetic. In conformity with the invention, the notchfree longitudinal edge 4 is folded back twice, each time by about and around the two longitudinal axes A-A and 8-8 so as to form a flange 5, FIG. 2, which is laterally offset with respect to the initial plane of sheet 1.

As shown in FIG. 3, if sheets of FIG. 2 are juxtaposed one against another, rather than a straight prism, one will obtain a volume of which thecontour perpendicular to'the successive sheets is concave,each sheet behaving like a chock of a thickness equal to-that of the sheet at one end but of a thickness a appreciably larger at the other and corresponding to the distance from the outer side of flange to the opposite side of the sheet which was not folded back. It is seen that when making use of a sufficient number of sheets 1 so fashioned, one may obtain a hollow cylinder closed on itself and of an inner radius c that may be arbitrarily selected by a suitable choice of sheets with respect to number and thickness.

If e is the initial thickness of the sheet, d the inner diameter of the cylinder (d and if D is the outer diameter (D 2(b+c)), one will have D/d a/e Because a must always not be less than 2e, D/d never may be less than 2 for this kind of folding.

In practice, the sheets 1 will be juxtaposed on a suitable mandrel on which the windings 6, FIG. 4, to be incorporated in the motor have been mounted, so that these automatically will be emplaced inside the finished inductor. The entirety may thereupon be impregnated or encapsulated in thermosetting or thermoplastic material 7, which thereby will ensure the entiretys fastening and solidification. Completion of the assembly will be obtained by mounting end shields 8 with bearings 9 supporting in gliding fashion armature 10, said endshields possibly being such as to encase sheets 1 and to retain the same radially. The armature proper may be of any suitable kind. In particular, it may consist of a ferromagnetic core 11 on which is mounted a tube 12 made of copper or any other good metallic conductor.

Fastening of end-shields 8 may be performed in any suitable manner. In particular, the inductor may be enclosed in a metallic shell at the ends of which the shields will be held by screws, bolts, rivets or in any other manner.

It may be seen furthermore that it will be possibly advantageous if the flange 5 of each sheet is oriented in a plane parallel to that of the non-folded side of the next sheet, against which it will then lie perfectly flat and thereby improve stability.

It will also be noted that the cylinder constituted by sheets 1 is discontinuous in the meaning of comprising longitudinal spaces between successive sheets. Their presence actually is an advantage because they allow passage to connections which otherwise would require boreholes difficult to achieve. Furthermore they facilitate ventilation.

FIG. 5 shows a variation in which an intermediate sheet 1' with non-folded edges is inserted between two sheets with flanged edges. This intermediate sheet therefore protrudes radially and, during the encapsulating operation, the projections may be allowed to extend beyond the insulation coating so as to act as a cooling fin. In this instance, the continuity of the peripheral sheathing may be ensured by providing for suitable perforations or notches in said projecting part that will allow interconnecting the successive segments of said sheathing. Obviously this entirety may be surrounded by a shell for which the spaces between said protruding parts of the sheets 1 then would act as ventilation ducts.

FIGS. 6 and 7 emphasize a characteristic already visible in FIG. 6. If a sheet with a non-flanged edge, or with an edge yet to be flanged, is considered, the height f of the iron from the bottom of the notches 2 to the opposite edge 4 determines the useful segment as regards closing the flux circuit between two successive teeth 3.

If the sheet were not folded back, the field source radial thickness would be B, FIG. 6. But because of flanging, the dimension f becomes f, FIG. 7, and the radial thickness therefore is reduced to without thereby reducing concomitantly the useful iron segment between two successive teeth, thereby reducing the outer diameter and obviously representing an advantage with respect to bulk, at least with respect to the embodiment of FIG. 4 which lacks projecting sheets 1'.

FIGS. 8 through It) show another mode of assembly of the juxtaposed sheets on the assembly mandrel. In these cases, each sheet I is provided with a series of punched apertures la, FIG. 9, near its edge 4, which intersect the folding axes A and B. Once edge 4 has been folded, FIG. ll), these notches will form hollows which will give rise to the peripheral grooves lb upon assembly at mandrel 10, FIG. 8, said grooves allowing deposition of a weld bead offset from the outer surface, FIG. 11. This weld bead thus may be entirely submerged and non-protruding. It allows sheet assembly independently of any encapsulating and of the very end-shields 8, which may be dispensed with by providing for the bearings inside the inductor in such manner as will be explained below.

A variation allows housing a suitable binding means such as is shown in FIG. 12 by the reference 13a in lieu of a weld bead; such a binding means may be a band, ferrule, a collar, or a metal wire winding, etc.

Again as a variation, and in so far as salients along the periphery of the field source do not otherwise hamper, sheet assembly may be achieved by welding along the successive joints of the juxtaposed sheets.

FIG. 13 shows a variation in the way to flange the sheet edges. Each of the sheets is provided with a longitudinal rib 10 near said edges, said rib projecting on one side. By alternately arranging the successive sheets in one direction and in the other, one achieves in causing an apparent excess-thickness of the sheets near said edges by means of those ribs, 10, again obtaining a cylinder. It will be noted that in such an arrangement, the sheets lie against each other in pairs, except where the ribs are located. While obviously the advantages stressed by reference to FIGS. 6 and 7 are thus lost, such arrangement does however allow on the other hand the manufacture of inductors wherein the ratio D/d will be less than 2.

FIG. 14 shows a variation in which each sheet 1 comprises two opposite ribs 1d and 1e, whereby all sheets may be kept apart from one another between the inner periphery of the inductor and the ribs.

Successive bosses might be used in lieu of continuous longitudinal ribs as regards the embodiments of FIGS. 13 and 14.

As regards the embodiment of FIG. 4, the bearings 9 of armature 10 have been shown as being of one piece with the endshields 8. Now it may be advantageous to make use of plastic bearings with low friction coefficients (nylon, polytetrafluoroethylene). In such a case the bearings may be directly force-fitted against the end of the magnetic circuit as shown in FIG. 15 where such a bearing is referenced by 14; in order to allow its assembly, sheets 1, or 1, are each provided at their ends with a notch 1f of suitable diameter so as to achieve a bearing housing.

FIG. 16 shows a variation wherein the notch, which in this instance is referenced as lg, does not end facing the magnetic circuit. For such an arrangement, bearing 15 must be first so placed on the sheet assembly mandrel as to be encased in the overall assembly.

FIG. 17 shows yet another embodiment in which bearings for the sliding support of armature are in the form of annular chocks 16 for closing certain of the notches 2. In such a case, the concerned windings are mounted on the chocks which themselves were first placed on the assembly mandrel. Once assembly has been completed, and the chocks and windings have been properly impregnated, both the latter will form a mass which is rigidly connected to the magnetic shell and in which the armature 10 may easily slide. Depending on the particular case, one may provide an arbitrary number of chocks 16 within the limit of the number of notches 2. It will suffice to put a reamer or a spindle through the set of chocks 16 so as to ensure their centering along the axis of the armature.

FIG. 18 shows an arrangement deriving from the previous one. In this instance each winding 6 is on an annular insulating spool 17 with which it is to be mounted inside a notch 2. A ring 18 of a material suitable to form a bearing is glued into the opening of that spoolsupport. It will be clear by inspection that ring 18, which also may be of minor thickness, might be made integral with the base of support 17 if the latter is made of an insulating material with the proper friction properties.

It will be seen furthermore that the arrangements of FIGS. 13 through 18 allow dispensing with the endshields such as 8 or reducing their function to shielding off dust or other foreign bodies.

Lastly, FIG. 19 shows an arrangement in which a bearing is force-fitted into a central opening 8a provided in each end-shield 8. This is an embodiment similar to that of FIG. 4, except that each bearing is constituted by a plastic sleeve 19 insert. In the example shown, the magnetic shell, constituted by the assembly of the sheets 1 and the windings 6, is assumed surrounded by a frame comprising a cylindrical sheath 20 to which are rigidly mounted cooling fins 21. This frame protrudes somewhat beyond the sheets 1 so as to define a centering space for the shields 8. The latter may be fastened to the frame by any appropriate means such as a force-fitted assembly, by tightening tie rods so as to press these shields against the frame, or radial screws through the frame and gripping shield shoulders, etc.

I claim:

1. An annular inductor component for an electric motor of the linear type wherein the motor armature is mounted for sliding movement within the central opening provided in said inductor component, said inductor component being constituted by an annular assembly of radially extending and essentially flat adjacent sheets of ferro-magnetic material, said sheets having their inner edges notched to establish circumferential recesses for receiving the motor windings and the radially outer portions of at least some of said sheets being deformed in a direction perpendicular to the plane of the sheet to establish spaces between them and adjacent sheets in contact therewith.

2. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the deformations in the radially outer portions of said sheets are established by a double consecutive folding of the outer edge portions thereof.

3. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the deformations in the radially outer portions of said sheets are established by ribs provided thereon.

4. An annular inductor component for an electric motor of the linear type as defined in claim 3 wherein the rib provided on one sheet engages the rib provided on an adjacently positioned sheet.

5. An annular inductor component for an electric motor of the linear type as defined in claim 3 wherein each sheet is provided with two radially spaced ribs facing in opposite directions from the plane of the sheet.

6. An annular inductor component for an electric motor of the linear type as defined in claim 1 where the radially outer portions of all of said sheets are deformed in adirection perpendicular to the plane of the sheet.

7. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein those sheets whose radially outer portions are deformed in a direction perpendicular to the plane of the sheet are separated by sheets whose radially outer portions are not deformed and which extend radially beyond the edges of said deformed sheets to establish cooling fins.

8. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the radially outer portions of said sheets are provided with identically located notches which establish a peripheral groove in said sheet assembly, and means engaged in said groove for securing said sheets together in their assembled relation.

9. An annular inductor component for an electric motor of the linear type as defined in claim 8 wherein said means which engages said groove is constituted by a weld bead.

10. An annular inductor component for an electric motor of the linear type as defined in claim 8 wherein said means which engages said groove is constituted by a binding device such as a metallic band, a non-metallic band, a shrinking ring, a ferrule, a collar or wire binding.

11. An annular inductor component for an electric motor of the linear type as described in claim 1 wherein some of said motor windings are located on annular spools of insulating material disposed in said notches provided at the inner edges of said sheets, and a ring of bearing material seated in the opening within each said spool and which establishes a sleeve type bearing for the motor armature.

12. An annular inductor component for an electric motor as defined in claim 11 wherein said annular spools are made of suitable insulating and friction material, and their inner bores serve as sleeve bearings.

13. An annular inductor component for an electric motor of the linear type as defined in claim 1 and which further includes end-shields disposed at the opposite ends of said annular sheet assembly, and through which the motor armature passes, and bearing means for said armature carried by each of said end-shields.

14. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the inner edges of said sheets are provided with additional notches at the opposite ends thereof to establish circumferential recesses in which sleeve type bearings for said armature are seated.

15. An annular inductor component for an electric cumferential recesses in which also are located the motor of the linear type as defined in claim 1 wherein windings of the motor and stand for closing means of sleeve type bearings for supporting said armature are the same.

seated in at least some of the longitudinally spaced cir- 

1. An annular inductor component for an electric motor of the linear type wherein the motor armature is mounted for sliding movement within the central opening provided in said inductor component, said inductor component being constituted by an annular assembly of radially extending and essentially flat adjacent sheets of ferro-magnetic material, said sheets having their inner edges notched to establish circumferential recesses for receiving the motor windings and the radially outer portions of at least some of said sheets being deformed in a direction perpendicular to the plane of the sheet to establish spaces between them and adjacent sheets in contact therewith.
 2. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the deformations in the radially outer portions of said sheets are established by a double consecutive folding of the outer edge portions thereof.
 3. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the deformations in the radially outer portions of said sheets are established by ribs provided thereon.
 4. An annular inductor component for an electric motor of the linear type as defined in claim 3 wherein the rib provided on one sheet engages the rib provided on an adjacently positioned sheet.
 5. An annular inductor component for an electric motor of the linear type as defined in claim 3 wherein each sheet is provided with two radially spaced ribs facing in opposite directions from the plane of the sheet.
 6. An annular inductor component for an electric motor of the linear type as defined in claim 1 where the radially outer portions of all of said sheets are deformed in a direction perpendicular to the plane of the sheet.
 7. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein those sheets whose radially outer portiOns are deformed in a direction perpendicular to the plane of the sheet are separated by sheets whose radially outer portions are not deformed and which extend radially beyond the edges of said deformed sheets to establish cooling fins.
 8. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the radially outer portions of said sheets are provided with identically located notches which establish a peripheral groove in said sheet assembly, and means engaged in said groove for securing said sheets together in their assembled relation.
 9. An annular inductor component for an electric motor of the linear type as defined in claim 8 wherein said means which engages said groove is constituted by a weld bead.
 10. An annular inductor component for an electric motor of the linear type as defined in claim 8 wherein said means which engages said groove is constituted by a binding device such as a metallic band, a non-metallic band, a shrinking ring, a ferrule, a collar or wire binding.
 11. An annular inductor component for an electric motor of the linear type as described in claim 1 wherein some of said motor windings are located on annular spools of insulating material disposed in said notches provided at the inner edges of said sheets, and a ring of bearing material seated in the opening within each said spool and which establishes a sleeve type bearing for the motor armature.
 12. An annular inductor component for an electric motor as defined in claim 11 wherein said annular spools are made of suitable insulating and friction material, and their inner bores serve as sleeve bearings.
 13. An annular inductor component for an electric motor of the linear type as defined in claim 1 and which further includes end-shields disposed at the opposite ends of said annular sheet assembly, and through which the motor armature passes, and bearing means for said armature carried by each of said end-shields.
 14. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein the inner edges of said sheets are provided with additional notches at the opposite ends thereof to establish circumferential recesses in which sleeve type bearings for said armature are seated.
 15. An annular inductor component for an electric motor of the linear type as defined in claim 1 wherein sleeve type bearings for supporting said armature are seated in at least some of the longitudinally spaced circumferential recesses in which also are located the windings of the motor and stand for closing means of the same. 